Window confirm() method throws a JS error when used in a metabox

[kmgalanakis]

When creating a metabox the content of it is sandboxed. If this metabox contains a button that when clicked it asks for a user confirmation using the Window confirm() method, a JS error is thrown stating that:

Ignored call to 'confirm()'. The document is sandboxed, and the 'allow-modals' keyword is not set.

On the test code below, I'm adding the custom metabox, which contains a button. Then I'm enqueuing a small JS script that handles the click of that button and asks for the user confirmation.

Test code

add_action( 'admin_head', 'my_meta_box' );
function my_meta_box() {
	global $post;
	add_meta_box(
		'my_meta_box',
		__( 'My metabox', 'my-context' ),
		'my_meta_box_callback',
		$post->post_type, 'side'
	);
}

function my_meta_box_callback() {
	echo '<p>Lorem ipsum dolor sit amet.</p>';
	echo '<button type="button" class="js-click-class">Click Me!</button>';
}

add_action( 'admin_footer', 'custom_admin_js' );
function custom_admin_js() {
    $script = '
         jQuery(".js-click-class").on("click", function () {
            confirm( "Are you sure you want to continue?" );
        });
    ';
	echo '<script type="text/javascript">' . $script . '</script>';
}

[BE-Webdesign]

Hi kmgalanakis,

Should be relatively easy to work around. Thank you for the detailed report.